In July of 2008, WSCI began its 11th project for the City of San Diego. WSCI was selected to complete the $24 million dollar, two-phase upgrade of the Otay Water Treatment Plant. This plant services one of the three major water service areas, providing 34 MGD of potable water to customers primarily in the southern reaches of the city.

Phase I of the Otay WTP Upgrades included construction of a new flocculation and sedimentation basin with three stages of flocculation, a sludge removal system and plate settlers. Sixteen existing dual media gravity filters were rehabilitated by providing a new pumped backwash system and filter-to-waste system. The team also replaced the under drain, media, and the surface wash system.

Phase II of the expansion included construction of a new chlorine dioxide contactor with a rapid mixer accompanied by a chlorine dioxide generator and feed system. This also included a new powder-activated carbon feed system, with chemical and sampling modifications.This project, necessary to meet and exceed stricter federal and state drinking water regulations, provided a state-of-the art facility with increased performance, quality, and reliability to the facility. It sustains clean drinking water for the ever growing population in the area.